Reduced Activity of von Willebrand Factor after Flow-Diverting Stent Implantation for Intracranial Aneurysms: A Link to Acquired von Willebrand Disease?

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Fig 1.
Scatterplots extracted from 32 patients treated by FDS only (closed circles) show a comparison of RISTO (ie, whole blood ristocetin-induced platelet aggregation) change with the volume (A) and morphologic index (B) of the aneurysm depicted on the x-axis. Open circles denote 6 patients treated by coiling + FDS, and x denotes 1 fusiform aneurysm; all have actually reduced vWF activity. The patient with delayed aneurysmal bleeding after FDS implantation is designated by (ruptured).
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Fig 2.
Receiver operating characteristic (ROC) curves for all aneurysm variables. Volume and morphologic index of the aneurysm have the highest discriminative ability. See also Table 5. MI indicates morphologic index.

Table 1:

Treatment variables in the reduced and nonreduced vWF groups

Characteristic	Reduced vWF (%)	Nonreduced vWF (%)	All (%)	P Value
Patient No.	9	23	32
Mean age (yr)	59.4 ± 5.6	46.8 ± 11	50.3 ± 11.3	.003
Sex (female)	7 (77.7)	17 (73.9)	24 (75)	.869
Mean aneurysm No.	1.56 ± 0.7	1.61 ± 0.5	1.59 ± 0.6	.742
Aneurysm frequency
1 aneurysm/patient	5 (55.6)	13 (56.5)	18 (56.3)	.559
2 aneurysms/patient	3 (33.3)	9 (39.1)	12 (37.5)	.564
3 aneurysms/patient	1 (11.1)	1 (4.4)	2 (6.2)	.826
FDS frequency
1 stent/patient	5 (55.6)	17 (73.9)	22 (68.7)	.566
2 stents/patient	3 (33.3)	5 (21.7)	8 (25)	.581
3 stents/patient	1 (11.1)	1 (4.4)	2 (6.3)	.294

Table 2:

Multiplate aggregometry results in all 32 patients

Aggregometry	Initial (Mean)	Last (Mean)	P Value	Normal Range^{^a}
ADP	13.34 ± 5.4	11.97 ± 5.2	.096	53–122
ASPI	12.0 ± 5.0	12.78 ± 6.4	.537	74–136
TRAP	57.34 ± 23.6	60.0 ± 26.6	.524	94–156
RISTOtest	31.88 ± 17.9	38.66 ± 20.3	.024	90–201

Note:—ASPI indicates test for aspirin responsiveness; TRAP, test for general performance of platelet and its glycoprotein IIb/IIIa receptor; RISTO, test for whole blood ristocetin-induced platelet aggregation.
↵a According to the manufacturer.

Table 3:

Multiplate aggregometry results among the reduced and nonreduced vWF groups

Multiplate Aggregometry	Reduced vWF (Mean) (n = 9)	Nonreduced vWF (Mean) (n = 23)	P Value
ADPin	14.78 ± 5.5	12.78 ± 5.4	.433
ADPlast	12.33 ± 6	11.83 ± 5.1	.681
ASPIin	11.67 ± 5.6	12.13 ± 4.9	1.000
ASPIlast	14.56 ± 6.5	12.09 ± 6.4	.341
TRAPin	59.11 ± 25.3	56.65 ± 23.5	.837
TRAPlast	50.44 ± 16.2	63.74 ± 29.2	.229
RISTOin	43.44 ± 21.9	27.35 ± 14.3	.103
RISTOlast	29.22 ± 18.1	42.35 ± 20.3	.094
RISTOchange	–(14.22 ± 12.3)	+(15.0 ± 11.3)	.000
RISTOchange (range)	–43 to –4	+1 to +39

Note:—-in indicates initial; -last, last; ASPI, test for aspirin responsiveness; TRAP, test for general performance of platelet and its glycoprotein IIb/IIIa receptor; RISTO, test for whole blood ristocetin-induced platelet aggregation.

Table 4:

Morphologic variables of aneurysms in the reduced and nonreduced vWF groups

Morphologic Variables	Reduced vWF (Mean) (n = 9)	Nonreduced vWF (Mean) (n = 23)	P Value
Neck area	41.35 ± 32.89	11.44 ± 6.13	.000
Volume	894.09 ± 1010.45	82.33 ± 81.37	.000
Volume-to-neck area	37.11 ± 49.4	9.65 ± 7.12	.001
Aspect ratio	1.72 ± 0.74	1.31 ± 0.43	.103
Size ratio	6.36 ± 7.15	1.68 ± 1.0	.000
Morphologic index	30,515.58 ± 28,234.38	1042.84 ± 1641.06	.000

Table 5:

Cutoff values of aneurysm variables according to the ROC analysis

Morphologic Variables	AUC	Threshold Value	Sensitivity (%)	Specificity (%)	95% Confidence Intervals	P Value
Neck area	0.908	18.35	78	79	0.800–1.000	.000
Volume	0.990	256	89	96	0.966–1.000	.000
Volume-to-neck area	0.870	13.67	89	78	0.736–1.000	.001
Aspect ratio	0.691	1.47	67	65	0.486–0.895	.098
Size ratio	0.908	2.16	89	78	0.807–1.000	.000
Morphologic index	0.990	4343	89	91	0.965–1.000	.000